Siloxane polymers and copolymers as barrier coatings and method of producing barrier coating properties therewith

ABSTRACT

A method of imubing polymer films as of polyethylene and polypropylene with gas, aroma, fragrance, flavor, grease and oil impermeable surface characteristics involving coating the film with appropriate silane compounds and cross-linking the same while providing physical adsorption adherence to the film, and in sufficient coating micron thickness to produce gas and related barrier characteristics; with chemical grafting, including by eb techniques, further providing improved bonding. Preferred barrier-coated polymer films with reduced haze and clarity are formed by such method. The method is also useful to increase the barrier properties of organo-polymer films that already possess initial barrier characteristics.

The present invention relates to novel barrier coatings and methods fororganic polymer films such as polyethylene and polypropylene films andthe like, wherein the coated films become imbued with reducedpermeability to gases, such as oxygen, air and carbon dioxide, as wellas to greases and oils.

In my earlier U.S. Pat. No. 4,803,126 there is disclosed a successfultechnique for applying polymer coatings, such as latex polymers havingthe desired barrier properties, to the surface of a polyolefin filmwhich had been treated with an organosilane primer coating, usingelectron beam radiation to graft the silane to the film and to bond thepolymer coating to the crosslinked silane primer coating.

While earlier noted in preliminary private tests, it has now beensurprisingly and repeatedly confirmed that appropriate silane primercoatings can provide remarkable barrier properties in and of themselves,and without additional coatings thereupon, to render the polymer film towhich the coating has been applied strikingly less permeable to gases,such as oxygen, and to aroma and flavor transmission, and to such adegree of impermeability that the coated film is admirably useful forsuch purposes as food packaging and shelf life extension thereof and thelike. In addition, improvement in the haze reduction, clarity andappearance of the film fortuitously concurrently occurs, matching thesurface quality of high grade "Mylar" film and the like, and alsoproviding improved dielectric performance for electrical uses, as well,as in electrical capacitors, for example.

Underlying the invention, therefore, is the surprising discovery thatappropriate polysiloxane coatings upon such polymer films aspolyethylene and polypropylene can provide for greatly decreasedpermeability in the films to gases, including oxygen and carbon dioxide,and to oils and greases, as well--and all as distinguished from priorutilizations of silane materials just to modify surfaces to improveadhesion or to couple polymers-to-polymers or to mineral fibers, asdescribed in the publications referenced in my said patent, or toimprove surface properties for bonding as in said patent. In "SilaneCoupling Agents", by Edwin P. Plueddemann of Dow Corning Corporation(Plenum Press), 1982, for example, the use of silane primarily as acoupling agent in mineral filled organic resin composites and the likeis taught in Chapter 8. The use of silane to couple thermoplasticpolyolefins is suggested in the "Guide to Dow Corning Silane CouplingAgent", 1988, page 21.

The discovered remarkable oxygen barrier properties were not onlytotally unexpected from prior art experience with silane compounds, butin fact ran counter to prior expectations of those skilled in this artas to silane gas permeability. For example, it had been reported thatthe oxygen permeability of a silicone elastomer (a crosslinkedpolydimethylsiloxane) is a factor of about 80 times greater than that ofa butyl rubber (a crosslinked polyisobutylene).

An object of the invention, therefore, is to provide new and improvedbarrier-coated polymer films and a method of producing the same,involving the use of appropriate coatings of polysiloxane, andpreferably the grafting of the same to the film surface.

A further object is to provide food packaging materials ofpolysiloxane-coated polymer films with improved gas impermeability,reduced aroma and flavor transmission properties and improved surfaceappearance and clarity, as well.

Other and further objects will be explained hereinafter and are moreparticularly delineated in the appended claims.

In summary, the invention embodies a method of imbuing polymer films asof polyethylene and polypropylene with gas, aroma, fragrance, flavor,grease and oil impermeable surface characteristics involving coating thefilm with appropriate silane compounds and cross-linking the same whileproviding physical adsorption adherence to the film, and in sufficientcoating micron thickness to produce gas and related barriercharacteristics; with chemical grafting, including by eb techniques,further providing improved bonding. Preferred barrier-coated polymerfilms with reduced haze and clarity are formed by such method. Preferreddetails and best mode embodiments are later presented.

The invention will now be explained in connection with the accompanyingdrawings:

FIG. 1 of which is a graph plotting experimental results contrasting thepermeability of polymer films to oxygen as a function of thickness ofpolysiloxane primer coating;

FIG. 2 contrasts the polysiloxane primer coating O₂ -permeabilitycharacteristics as a function of temperature with present-day barrierfilms, the data as to the latter having been presented by H. Watanabe in"The Use of High Barrier Packaging Films, etc.", Future-Pax '88, SixthInternational Ryder Conference on Packaging Innovations, Sept. 14-16,1988; and

FIGS. 3A and 3B are respectively scanning electron micrographs of thesurface of polyethylene film prior and subsequent to coating with asiloxane coating of the invention.

METHOD OF PREPARATION

In accordance with the invention, the useful siloxane polymers areprepared by hydrolysis of silane monomers, and mixture of monomers whena copolymer film is desired, in an aqueous alcohol solution. The mixtureis allowed to stand for about 24 hours at 25 degrees C. to equilibratethe oligomeric siloxane structures, whereupon the alcohol solutioncontaining the oligomeric siloxane structures is coated on the polymerfilm surface and is dried, preferably in a stream of warm air, toevaporate the alcohol and water to complete the formation of theSi--O--Si bonds of the polymer coating, highly cross-linking the same.

Optionally, but preferably, in order to improve adhesion and durabilityby providing chemical as well as physical bonding, the siloxane polymermay be grafted to the film surface when the siloxane polymer orcopolymer contains a double bond, by using either a conventionalpromoted peroxide cure, (of course, added to the siloxane primer priorto coating on the polymer film surface), or by electron-beam initiatedgrafting as described in my said prior patent.

Corona treatment of the polyolefin film prior to the siloxane coatinghas been found to improve the coating adhesion, as later discussed. Thefurther discovery of the necessary siloxane coating thickness ranges foreffective gas barrier performance is also detailed hereinafter.

The structures of the silanes found useful in the practice of thepresent invention are shown below: ##STR1##

The groups R1, R2, R3 and R4 may be the same or different and they areselected from the following groups:

1. Alkoxide groups, such as methoxy, ethoxy, propoxy, 2-methoxyethoxy,etc.;

2. Acid groups, such as acetoxy, propoxy, etc.;

3. Alkyl groups, such as methyl, ethyl, propyl, butyl, amyl, benzyl,cyclohexyl, and higher alkyl groups;

4. Aromatic groups, such as phenyl and alkylated phenyl groups,naphthyl, etc.;

5. Halogenated alkyl and aromatic groups, such as chloropropyl,1,1,1-trifluoromethyl, trifluoropropyl, pentafluorophenyl,3-(heptafluoroisopropoxy)propyl, 1H,1H, 2H,2H,perfluorodecyl, etc.;

6. Amine containing groups, such as 3-(2-aminoethylamino)propyl,gamma-aminopropyl, etc.;

7. Unsaturated groups such as allyl, gamma(methacryloxy) propyl, vinyl,gamma(acryloxy)propyl, 3-(2-vinylbenzylaminoethyl) propyl, etc.;

8. Epoxy containing groups such as 3-(2,3-epoxypropyloxy) propyl; and

9. Mercapto containing groups such as 3-mercaptopropyl.

The mechanism of gas permeation through a plastic film is a complexprocess involving adsorption on a surface, migration through the bulk ofthe film through pores in the film, and desorption from the other side.While the total mechanism by which the siloxane polymers and copolymersof this invention improve the barrier properties of the plastic films onwhich they are deposited is not fully understood, and applicant does notwish to be bound by the following theoretical explanation (it beingsufficient to teach how to obtain the results of the invention), it isbelieved that the siloxane polymers and copolymers of the invention wetthe surface of the polymer film smoothly and uniformly and mostly fillin the openings of the pores on the surface of the film. This keeps thegas molecules out of the pores so that even though the pores are stillthere, the gas molecules cannot get into the pores to pass through thebulk of the film.

Evidence supporting this hypothesis is provided in the scanning electronmicrographs of FIGS. 3A and 3B (10,000 magnification) which showrespectively the coarse rough surface of the untreated low densitypolyethylene film (LDPE) 125 microns thick, and the leveled and smoothsurface of the siloxane coated film (vinyl benzyl amine silane, DowCorning Z6032), approximately six microns thick. Further support iscontained in the data of later-described Table 1 which shows theremarkable haze reduction (from 14.9% down to 2.5%) resulting from thesmoothing and wetting of the film surface by the primer, which reducesthe multiple light reflection and scatter.

It is also recognized that the more closely the chains of a polymer willpack together, the better will be the barrier properties. For example,in current-day packaging films sold under the trademark "SARAN" of DowChemical Company, the chains of polyvinylidene chloride can packtogether very closely and it has excellent barrier properties.Similarly, the molecular configuration of poly(ethylene-vinyl alcohol)is held very close together by hydrogen bonding between the hydroxylgroups on adjacent polymer chains and these copolymers have good barrierproperties.

This close packing has the disadvantage, however, that the meltviscosity of these polymers is high and they must be extruded at hightemperatues, which can lead to thermal decomposition. Generally, acomonomer is added during polymerization of polyvinylidene chloridewhich serves to disturb the close packing and lower the melt viscosityand allow extrusion at lower temperatures. Unfortunately, this alsodegrades the barrier properties as well, as shown in the "SARAN" curvesof later-discussed FIG. 2.

In other present-day packaging films such as those of NorthernPetrochemical Company, sold under the mark "EVAL", the ethylene unitsincluded in the ethylene-vinyl alcohol copolymer tend to lower the meltviscosity of the vinyl alcohol polymer and allow extrusion attemperatues below the decomposition temperature of the polyvinyl alcoholpolymer. Increasing the ethylene content of the copolymer (the upper"EVAL" curve of FIG. 2, later discussed, wherein the ethylene content Eis 40% as distinguished from the lower E=32% "EVAL" curve), alsodegrades the barrier performance of the vinyl alcohol polymer. Thispolymer also suffers from the disadvantage that it is hygroscopic; andwater plasticizes the polymer and seriously degrades the performance ofethylene-vinyl alcohol polymers as barrier coatings.

Close packing of polymer chains to prevent gas and oil molecules frompenetrating the polymer can also be achieved by crosslinking the polymerchains. However, highly crosslinked polymers are very rigid andextremely difficult to process by melt extrusion.

One of the advantages of the polymers and copolymers of the invention,on the other hand, is that the hydrolyzed oligomers are soluble inalcohol solution, so they are easily applied to the surface of the basefilm by a simple coating technique. The polymerization and cross-linkingof the siloxane coating is completed by drying the coating, preferablyat a slightly elevated temperature, to remove alcohol and water. The useof this alcohol technique enables the generation of a highlycross-linked film coating structure, and no high temperature extrusionis required. The degree of crosslinking is controlled by the monomersthat are selected.

EXAMPLE 1

For example, hydrolyzed dimethyl dimethoxy silane will polymerize to alinear polymer. The length of the polymer chain can be controlled bycopolymerizing with trimethyl methoxy silane. This compound has only onesite which is reactive in the condensation polymerization and it will"cap" the growing polymer chain.

EXAMPLE 2

On the other hand, methyl trimethoxy silane has three reactive sitesduring the condensation polymerization and will crosslink betweengrowing polymer chains as well as branch when it is cohydrolyzed withdimethyl dimethoxy silane.

EXAMPLE 3

Similarly, tetraethoxy silane has four reactive sites and will produce avery highly crosslinked polymer when it is included in thepolymerization mixture.

In order to practice my invention, it is necessary to select a monomermixture which, subsequent to hydrolysis and application to the filmsurface, will smoothly and uniformly wet the film surface. We havedevised a test to select the siloxanes and mixtures of siloxanes whichare useful in the practice of the invention.

Test for Useful Siloxane(s)

A 10 ml quantity of a silane or a mixture of silanes is dissolved in 90ml of methyl alcohol and 1 ml of water is added and carefully mixed in.The solution is allowed to stand at about 25 degrees C. for 24 hours. Apiece of test film, for example low density polyethylene film if thecoating is to be used on polyolefin films, is immersed briefly in themethanol solution of the hydrolyzed silanes, and the alcohol is allowedto dry slowly in dry air. The coating is then warmed gently in a streamof air to complete the polymerization by driving off the water.

The silanes and mixtures of silanes that are useful in the practice ofthe present invention form a smooth and uniform coating on the surfaceof the organic film on which they are tested. These coatings also reducethe haze of the film.

The silanes and mixtures of silanes that are not useful in the practiceof the invention have been found to form beads and droplets of siloxaneon the surface of the film on which they are tested as the alcohol driesoff the surface of the film and thus fail to wet the same. Thesematerials thus do not form useful barrier coatings on organic polymerfilms.

It has been discovered that the silanes and silane mixtures that areuseful in the practice of this invention, particularly on polyethyleneand polypropylene films, generally contain a silane with an amino group.

EXAMPLE 4

For example, the vinylbenzylamine silane, Dow Corning Corp. Z-6032, whenhydrolyzed in alcohol solution and applied to a polyethylene filmsurface, formed a smooth continuous film which was useful as both abarrier to oxygen and oil.

EXAMPLE 5

In contrast, gamma-methacryloxypropyl trimethoxy silane by itself whenhydrolyzed in methanol solution and applied to a polyethylene film,formed beads of material which drew away from the film surface as thealcohol dried. This indicated that the siloxane oligomers did not wetthe surface of the polyethylene film and were thus not useful as barriercoatings on polyethylene film.

An equal volume mixture of the gamma-methacryloxy propyl trimethoxysilane and vinyl benzyl amine silane (Dow Corning Z6032) hydrolyzedtogether in methanol solution and when applied to the polyethylene filmsurface was found, however, to dry out in the form of a smooth, uniformcoating. This shows that the cohydrolyzed mixture is useful in thepractice of the invention.

EXAMPLE 6

Similarly, hydrolyzed methyl trimethoxy silane in alcohol formed beadson the surface of the polyethylene film when the alcohol evaporated.However, when the methyl trimethoxy silane was cohydrolyzed with thesaid vinyl-benzyl amine silane and applied to the polyethylene film, asmooth uniform coating was obtained.

"Wetting"

The reason why an amine-containing silane will wet the surface ofpolyethylene film is not fully known. It may be due in part to anegative electrical surface charge on the surface or just under thesurface of the film which attracts the cationic amine-containingsiloxane when it is in methanol solution. It is also possible that thecarboxyl groups on the film surface, particularly after it has beencorona treated, attract the amine groups on the siloxane and cause it towet the polyethylene film surface.

When mixtures of silanes which include an amino group containing silaneare to be used as barrier polymers on polyethylene or polypropylenefilm, it has been found that the monomers should be mixed and thencohydrolyzed in order that the resulting oligomers will wet the surface.

Thus, a mixture of equal volumes of the vinyl benzyl amine silane andthe methacryloxypropyl silane hydrolyzed separately, was found to formbeads on the surface of the polyethylene film as the alcohol solutionevaporated.

EXAMPLE 7

Similarly, a mixture of 9 parts of methyl trimethoxy silane and one partof the vinyl benzyl amine silane that had been cohydrolyzed in methanolformed a smooth, uniform coating on the surface of the polyethylenefilm.

In contrast, a mixture of equal parts of methanol solutions of the vinylbenzyl amine silane and the methyl trimethoxy silane that had beenseparately hydrolyzed, formed beads of material on the polyethylene asthe alcohol evaporated from the mixture after it was coated on thepolymer surface.

EXAMPLE 8

A 10 ml quantity of gamma aminopropyl triethoxy silane was dissolved in90 ml of methyl alcohol and one ml of water was added and carefullymixed in. The solution was allowed to stand for about 24 hours at about25 degrees C. A piece of polyethylene film was briefly immersed in thesolution and allowed to dry slowly in dry air. The coating was warmedgently in a stream of warm air to complete the polymerization. A smooth,uniform coating was formed on the polyethylene film surface.

EXAMPLE 9

A mixture of 2 ml of gamma-aminopropyl tri-ethoxy silane and 8 ml ofvinyl triethoxy silane was dissolved in 90 ml of methanol and 1 ml ofwater was added and carefully mixed in. The solution was allowed tostand for 24 hours at 25 degrees C.

A piece of polyethylene film was immersed in the solution and allowed todry slowly in dry air. The coating was warmed gently in a stream of warmair to complete the polymerization. A smooth, uniform coating was formedon the polyethylene film surface.

EXAMPLE 10

A mixture of 2 ml of gamma-aminopropyl tri-ethoxy silane and 2 ml ofmethyl triethoxy silane was dissolved in 90 ml of methanol and 1 ml ofwater was added and carefully mixed in. The solution was allowed tostand for 24 hours at 25 degrees C.

A piece of polyethylene film was immersed in the solution and allowed todry slowly in dry air. The coating was warmed gently in a stream of airto complete the polymerization. A smooth, uniform coating was formed onthe polyethylene film surface.

It has been discovered, furthermore, that the coating phenomenon hereindescribed is generally a surface-coating effect. Cross-sectionalanalysis of the LDPE coated film, for example, by scanning electronmicroscopy and electron-dispersive X-ray spectroscopy has revealed thefew micron coating to be attached to the film surface with no apparentpenetration into the film.

The surface and barrier properties of the barrier coating are controlledby the nature of the monomers that are used to form the oligomers. Forexample, the critical surface tension of a polyethylene film that hasbeen coated with hydrolyzed vinyl benzyl amine silane is about 55dynes/cm. In contrast, the critical surface tension of the coating onpolyethylene film which was prepared by hydrolyzing a mixture of 9 partsof methyl trimethoxy silane and one part of the vinyl benzyl aminesilane is only about 23 dynes/cm. A drop of hydrocarbon oil on thecoated surface has a large contact angle and did not spread. Incontrast, the oil spread slowly and wet the surface of the uncoatedfilm.

If it is desired to reduce the sensitivity of the coating to moisture,as another example, one may cohydrolyze the vinyl benzyl amine silanewith an alkyl trimethoxy silane in order to replace some of the amineand amine salt groups that are hydroscopic. Similar tailoring of theselected silane compounds for desired properties can be obtained withappropriate silane selections.

The adhesion of the coating on the film can be improved by incorporatingmonomers with vinyl unsaturation into the siloxane mixture beforehydrolysis and grafting the resulting coating to the film surface. Thegrafting can be accomplished by incorporating a conventional promotedfree radical generator in the coating (such as dicumyl peroxide, forexample) that will react upon gentle heating, or by use of electronbeam-initiated grafting, as described in my said patent, subsequent todrying of the coating.

The improved adhesion of the barrier coating to the substrate may, asbefore explained, be achieved by grafting the siloxane coating to thefilm. In the case of a barrier coating of a vinyl benzyl amine siloxaneon a polypropylene substrate, the "Scotch tape test" (described in mysaid prior patent) removed some of the ungrafted coating from thepolypropylene, but did not remove any of the grafted coating. Thisexperiment demonstrates the greatly improved adhesion of the coating tothe substrate that can be acheived by eb grafting.

The graph of the before-mentioned FIG. 1, demonstrates the efficacy ofsiloxane coatings applied to polymer films in accordance with theinvention, plotting O₂ permeability in cc/100 in² /24 hours at 23° C.along the ordinate, and siloxane primer thickness in microns along theabscissa for 38 micron oriented polypropylene (OPP), 135 micron lowdensity polyethylene film (LDPE) and 13 micron polyester (PET), with andwithout a coating derived from hydrolyzed 60% methanol and 40% DowCorning Z-6032 silane, prepared as above-described and applied invarious thicknesses to the film and electron-beam grafted with about 175KV and doses up to 5 Megarads as detailed in my prior patent. Theuncoated films were quite permeable (approximately 70-95 cc/100 in² /24hours); whereas coatings of from 5 to 22 microns provided excellent O₂-permeable barriers under approximately 2.5-0.5 cc/100 in² /24 hours atone atmosphere of pressure. Each of these coated films provided low hazeappearance as well, and outstanding aroma or fragrance retention ofproducts packaged therewith as later described in connection with theLimonene Transmission tests of Table 2; the coated films havingapparently reduced solubility of aroma and flavor compounds in suchpackaged food or other products--so-called "scalping" of such.

Gas permeability under 1 cc/100 in² /24 hours at room temperature andone atmosphere was realized with primer thicknesses of the order of 10microns. Thickness of a few microns thus provides a dramatic improvementin barrier properties. Equally impressive enhancement of oil resistanceof the polyolefins has also been demonstrated by the process.

Favorable comparison of the above siloxane primer barrier system("PRIMER") with present-day commercial food-packaging and similar filmmaterials in terms of O₂ permeability as a function of increasingtemperature, is presented in the before-mentioned FIG. 2. It will beobserved that the slope or temperature coefficient of the "PRIMER" curveis more favorable than for the DOW films known as "SARAN"(polyvinylidene chloride), and the films known as "EVAL" (NorthernPetrochemical Company--ethylene vinyl alcohol), and at least comparableto "BAREX" film.

The improvement in the before-mentioned haze appearance is shown in thefollowing Table 1, attained for the LDPE film with 5 micron siloxaneprimer bilaterally applied; and the marked improvement in LimoneneTransmission for both the coated LDPE and OPP films is presented inTable 2.

                  TABLE 1                                                         ______________________________________                                        HAZE MEASUREMENTS - LDPE                                                      135 MICRON FILM:5 MICRON                                                      PRIMER BILATERIAL                                                             ASTM TEST METHOD D-1003                                                                      TRANSMITTANCE  HAZE                                            SAMPLE         %              %                                               ______________________________________                                        VIRGIN FILM    88.8           14.9                                            PRIMED FILM    88.9           2.5                                             ______________________________________                                    

                                      TABLE 2                                     __________________________________________________________________________    LIMONENE TRANSMISSION - LDPE/OPP                                              ASTM TEST METHOD D-1653                                                       (75° F. - 35% R.H.)                                                                          LOSS                                                    SAMPLE   THICKNESS    (MG/100 IN.sup.2 /24 HOURS)                                                                NORMALIZED                                 __________________________________________________________________________    VIRGIN LDPE                                                                            135 MICRON   8014.9       100.0                                      PRIMED LDPE                                                                            APPROX. 145 MICRON                                                                         6.0          .07                                        VIRGIN OPP                                                                             50 MICRON    3359.6       100.0                                      PRIMED OPP                                                                             APPROX. 60 MICRON                                                                          31.8         .94                                        __________________________________________________________________________

The Limonene Transmission test (D-1653) is an accepted measure of aromaor fragrance or flavor transmission as used in the food-packagingindustry, involving gas chromatograph measurement of limonene solubilityin the film. Table 2 demonstrates that for the LDPE film with thesiloxane coating above described, the limonene loss was only 6 mg/100in² /24 hours as contrasted with the more than thousand times greaterloss (8014.9) for the uncoated or virgin LDPE. Similar tremendousfragrance retention was achieved with the coated OPP film.

While the above examples have been principally carried out withmethanol, selected because of its ease of use and relatively low boilingpoint and because it is an excellent solvent for both silanes and water,other solvents miscible with water and of high vapor pressure forevaporation and that can dissolve a wide range of silanes may also beused, including other alcohols such as ethanol and isopropyl alcohol.Further modifications will occur to those skilled in this art and suchare considered to fall within the spirit and scope of the invention asdefined in the appended claims.

What is claimed is:
 1. A method of rendering organic polymer filmssubstantially impermeable to gases such as oxygen, aroma, flavor andfragrance, and greases and oils, that comprises, hydrolyzing silanemonomers or mixtures of silane monomers in an aqueous alcohol solutionand equilibrating the same; coating the same upon the polymer film; andevaporating the alcohol and water to complete the formation of Si--O--Sibonds and to cross-link the silane(s), thereby to produce a siloxanegas-impermeable barrier coating adhered to the surface of the film; andin which the further step is performed of chemically grafting saidsiloxane coating to the film.
 2. A method as claimed in claim 1 and inwhich the grafting is effected with electron beam radiation.
 3. A methodas claimed in claim 1 or 2 and in which the alcohol is methanol and thesilane(s) are represented by the following formula: ##STR2## where thegroups R1, R2, R3 and R4 may be the same or different and are selectedfrom the following groups:
 1. Alkoxide groups, such as methoxy, ethoxy,propoxy, 2-methoxyethoxy, etc.;2. Acid groups, such as acetoxy, propoxy,etc.;
 3. Alkyl groups, such as methyl, ethyl, propyl, butyl, amyl,benzyl, cyclohexyl, and higher alkyl groups;
 4. 4. Aromatic groups, suchas phenyl and alkylated phenyl groups, naphthyl, etc.;5. Halogenatedalkyl and aromatic groups, such as chloropropyl, 1,1,1-trifluoromethyl,trifluoropropyl, pentafluorophenyl, 3-(heptafluoroisopropoxy),1H,1H,2H,2H, perfluorodecyl, etc.;
 6. Amine containing groups, such as3-(2-aminoethylamino)propyl, gamma-aminopropyl, etc.;
 7. Unsaturatedgroups such as allyl, gamma(methacryloxy) propyl, vinyl,gamma(acryloxy)propyl, 3-(2-vinylbenzylaminoethyl) propyl, etc.; 8.Epoxy containing groups such as 3-(2,3-epoxypropyloxy) propyl; and 9.Mercapto containing groups such as 3-mercaptopropyl.
 4. A method asclaimed in claim 1 and in which the silane comprises a vinyl benzylamine silane.
 5. A method as claimed in claim 4 and in which the vinylbenzyl amine silane is cohydrolyzed with methyl trimethoxy silane.
 6. Amethod as claimed in claim 5 and in which the ratios of said silanes byvolume range from about 9 to
 1. 7. A method as claimed in claim 1 and inwhich the silane comprises gamma aminopropyl triethoxysilane.
 8. Amethod as claimed in claim 1 and in which the siloxane coating isapplied in a thickness of the order of a few microns.
 9. A method asclaimed in claim 8 and in which the said thickness lies within the rangeof from about 5 to 22 microns.
 10. A method as claimed in claim 1 and inwhich the grafting is effected by peroxide cure.
 11. A polymer filmconstituted of an organic polymer film base to a surface of which isphysically adsorbed a cross-linked siloxane non-electrically conductivecoating that imbues the said surface with gas, aroma, flavor andfragrance and grease and oil impermeable surface characteristics, and inwhich the said coating is produced by the method of claim
 1. 12. Apolymer film as claimed in claim 11 and in which the said coating is ofthickness in the range of about 5 to 22 microns.
 13. A polymer film asclaimed in claim 11 and in which the said coating imparts haze-reductioncharacteristics and clarity.
 14. A polymer film as claimed in claim 11and in which the silane precursor of the siloxane comprises a vinylbenzyl amine silane.
 15. A polymer film as claimed in claim 14 and inwhich the vinyl benzyl amine silane is cohydrolyzed with methyltrimethoxy silane.
 16. A polymer film as claimed in claim 15 and inwhich the ratios of said silanes by volume range from about 9 to
 1. 17.A polymer film as claimed in claim 11 and in which the silane precursorof the siloxane comprises gamma aminopropyltriethoxy silane.